UK internet shoppers to spend £4,000 a second

Record day expected as office workers spend lunch-time shopping from their desks

The internet will be jammed with traffic tomorrow lunchtime as millions of shoppers log on to do their Christmas shopping, making it the biggest spending day ever in the cyber market.

Eager gift buyers are expected to spend £4,000 per second throughout the day on this year's must-haves, which include iPhones, Susan Boyle's debut album and the new Harry Potter Half-Blood Prince dvd.

"It's the biggest day in terms of sales – the first Monday in December is the big day as most people have been paid," said David Smith, director of operations at IMRG, the industry body for online retailers, which predicts that consumers will spend £350m tomorrow, almost 10% up on last year.

The majority of sales are likely to be made by office workers taking advantage of faster broadband speeds at work – with traffic expected to spike between 9am and 10am and again at lunchtime on what is referred to as cyber Monday.

A recent survey by the moneysaving website VoucherCodes.co.uk calculated that businesses would lose £1.4bn a week between now and Christmas as a result of reduced productivity, with 70% of employees spending time shopping for gifts instead of working. The research found that a fifth of workers spent 10 hours a week in shopping online.

"Everyone decides what they are going to buy over the weekend then goes to work on Monday, gets on the computer and makes their purchases," said Andy Street, managing director of John Lewis, which expects sales of £4.5m on the day – five times more than a normal Monday.

Marks & Spencer, which has taken on extra staff in its warehouses and call centres to handle the expected surge in orders, expects more than 3.5 million people to log on to its website tomorrow. Last year Amazon received 1.4 million orders in 24 hours – the equivalent of 16 every second – on 8 December, its busiest day of the year. This year the giant online operation is anticipating its busiest Christmas on record with sales expected to increase by up to 35%, with the iPod Touch and Joseph Joseph chopping boards among the bestsellers.

There is less obvious discounting on the high street. Last December store groups had to move their sales forward after a collapse in consumer confidence hit revenue following the banking crisis. Increasingly, retailers are offering online-only promotions and stealth reductions of up to 50% through popular websites such as VoucherCodes.co.uk which promote the special internet deals and printable coupons from the likes of Argos, Tesco and Comet.

James Carter, who runs vouchercodes, said the number of deals available though the site had increased by almost 90% this year. "Retailers use us to bring forward sales and generate interest from consumers," he said. "Shoppers are much more savvy now." Current deals include 25% off Monsoon orders and 20% at Dorothy Perkins.

IMRG said consumers had not been put off shopping online by the recent Royal Mail strikes.

While the crowds on high streets and in shopping centres across the UK will not peak until the final Saturday before Christmas, internet sales do so earlier to factor in delivery times.

Consumers are now as happy buying clothing and homeware online, with M&S and Next among the most searched for, whereas previously consumers stuck to safe online purchases such as books, fridges and TVs.